Some Aspects of Sexual Behavior in Domestic Sheep, Ovis Aries

Abstract

Abstract1. A generalized description of the motor components comprising male courtship is presented. Included among the major acts are a) nosing the perineum; b) nudging, a complex of several subacts including orientation behind the ewe, extension and flexion of one foreleg, tilting and lowering the head accompanied by a low-pitched vocalization and flicking of the tongue ; c) the Flehmen or lip curl, as displayed by the ram is described, but the signal function in this species is problematical; d) mounting accompanied by e) pelvic oscillations, f) intromission, and g) ejaculation, defined behaviorally as an especially deep thrust After-reactions may take the form of remounting the ewe, leaving to court another female, or standing while the just-mounted ewe leaves. 2. The motor components displayed by the ewe vary with its hormonal condition. When anestrus, the female manifests either passive or active avoidance depending upon the persistence of the ram. During the 15 to 28 hours of estrus, female motor activity ranges through a spectrum of low to high to low intensity responses. For the first 3-5 hours, low intensity acts include standing, head lowered and pinnae of ears somewhat flattened, swinging the head back to watch the courting ram, walking off and then standing and looking back at the ram. Persistent nudging by the ram at this time results in acceptance. From about the 5th to the 15th hours of estrus, the ewe is notably more aggressive. Soliciting behavior takes the form of approaching the ram, nuzzling and pushing its head into the flank and scrotal regions. Low intensity responses supervene from the 15th hour to the end of estrus, grading into the avoidance behavior characteristic of the anestrous ewe. 3. Observations of a small, closed flock comprised of 6 ewes and 1 ram in an indoor pen provided information on dominance relationships among the ewes and the influence of rank upon female sexual activity. Additional information obtained from these observations included evidence of memory by the ram of the identity of females with which he had mated. 4. The ontogenesis of male courtship acts was studied in a flock of 8 rams, 4 of which were unaltered, 2 castrated (one at 118 days, the other at 139 days of age), and 2 deprived of heterosexual contact until well past the age of physiological maturity. All unaltered rams achieved copulation, but only after from 10 to 20 ten-minute exposures to a stimulus ewe. One of the castrate rams succeeded in mating after 12 exposures, the other displayed no courtship behavior at the 20th exposure at which time he was 540 days old. Of the 2 female-deprived rams, one achieved a mating at the first exposure to an estrous ewe; he was 419 days old at the time. The other deprived ram evidenced successful courtship on the 12th exposure when he was 676 days of age. General observations of the ram flock revealed that all components of the male pattern, except for the consummatory acts of intromission and ejaculation were manifested during social interactions in the flock. Such behavior was displayed during the play activities of all except one of the castrate rams. 5. Three of these rams were further examined with the view of establishing the effect of injections of male hormone. Included in this study were the two castrates and one unaltered ram from the original flock of eight. The latter was castrated after having developed consistent, adult sexual behavior. Treatment began after all three rams displayed a decline to little or no sexual behavior in a test situation. In all three instances, treatment with exogenous androgen evoked the complete male courtship pattern, although one of the original castrates appeared to be almost refractory to the treatment. 6. A discussion of these findings is included in each of the various sections of this report.